Molecule test for display tunning and dns client

[strus38]

• Added molecule test in display_tuning.
• Added molecule test in dns_client - warning the testing is limited to linters since /etc/resolv.conf cannot be touched within a container.

[btravouillon]

Thanks for the PR. Added a few comments.
I still need to check the issue with dns_client/converge/resolv.conf before final review.

[btravouillon]

It's possible to run the dns_client role during converge within docker:

$ podman exec -it instance cat /etc/resolv.conf
#### Blue Banquise file ####
## Ansible managed: Do NOT edit this file manually!

search .localhost
nameserver 10.10.0.1 

To achieve this, umount the bind mounted /etc/resolv.conf in the prepare phase:

---
- name: Prepare
  hosts: all

  tasks: 
    - name: "Umount Docker's /etc/resolv.conf"
      mount:
        path: /etc/resolv.conf
        state: unmounted

[strus38]

All fixed. IT works like a charm now.

[btravouillon]

Approved. Thanks!

[oxedions]

OK for me.